Chrysanthemum dwarf class virus disease is how the disease test and quarantine?

There are 3 main testing methods: (1) embedded wood budding. Take two stem inserts of the plant to be examined, graft them onto both sides of the buds of the indicator plant, chrysanthemum Mistletoe variety (15-20cm high), remove the plant parts above the bud joints, and the buds will grow gradually at 22℃, and typical symptoms will appear after 4-5 weeks. (2) Sap inoculation method. The sap of the infested plant is inoculated with guayule, and the judgment is made according to the symptoms. Although this method is simple, it is not as reliable and accurate as bud-joining. (3) CSVd laboratory rapid test method. These include the "two-way" polyacrylamide gel electrophoresis recommended by the EPPO (OEPP/EPPO, 1989), which can be completed in less than 1 d, with accurate and reliable results. Identification of hosts: different varieties of chrysanthemum: Chrysanthemum. cv. Mistletoe severely dwarfed, with greenish spots on leaves (Keller, 1951); Misdtltoe varieties, grafted onto dwarfed scions, which produce a herpetic pattern after 6 weeks, with curling of the leaves and the appearance of yellow, subcircular spots, which can be up to 7 mm in diameter in summer, but are much smaller in winter, and the plant is slightly affected. Leaf crumpling; Blazing.Gold varieties of leaves appear scattered yellow discoloration along the veins; Bonnie.Jean and Sunfire and other varieties, inoculation 2 ~ 3 weeks after the production of inconspicuous symptoms; melaleuca: inoculation 30d after the leaves appeared localized spots, but the symptoms are not stable. In vitro stability: ① Blunting temperature. 95～98℃ (Hollings.and.Stone, 1973). ② Dilution endpoint. 10-3～10-5 (Hollings.and.Stone, 1973). (iii) In vitro survival. 2 to 3 months (Hollings. and. Stone, 1973), in dry diseased tissues, the virus-like infestation lasts for more than 2 years, and freezing tolerance for up to 1 year or more. Molecular biology assay: DIG-label.cRNA probe (Hataya, T.et.al., 1999), RT-PCR-ELISA (Menzel, W.et.al., 2000) and real-time.RT-PCR are reported with increasing sensitivity.Mumford, R.A.et.al. (2000) compared the sensitivity of the three methods and found that real-time.RT-PCR was the most sensitive, 100 times more sensitive than RT-PCR and 1000 times more sensitive than DIG-label.cRNA probe. Evaluation of quarantine risk: The pathogen of this disease, chrysanthemum dwarf-like virus, is a destructive disease of chrysanthemum, with 55% plant dwarfing in the year of infestation. Although there is no vector, the disease can spread through the branches, cuttings and seeds of the damaged chrysanthemums, and spread through pollen, which is extremely harmful to chrysanthemum production. When Jilian was evaluating the danger, the value of danger was 6 points and it was designated as a low-risk quarantine pest. Quarantine measures: Chrysanthemum cuttings used for propagation must be tested according to the quarantine procedure EPFO.24 and be free of CSVd parent plants and not exceed 3 generations (OEPP/EPPO, 1989). At least 30 plants must be observed during the flowering period, or 10% or more of the chrysanthemum cuttings must be observed and tested (OEPP/EPPO, 1990).